Frame Rate
NTSC system
delivers 29.97 frames/s or 59.94 fields/s.
24p
frame rate is also a noninterlaced format, and is now widely adopted by those planning on transferring a video signal to film. Film and video makers turn to 24p for the "cine"-look even if their productions are not going to be transferred to film, simply because of the "look" of the frame rate. When transferred to NTSC television, the rate is effectively slowed to 23.976 frame/s, and when transferred to PAL or SECAM it is sped up to 25 frame/s. 35 mm movie cameras use a standard exposure rate of 24 frames per second, though many cameras offer rates of 23.976 frame/s for NTSC television and 25 frame/s for PAL/SECAM. The 24 frame/s rate became the de facto standard for sound motion pictures in the mid-1920s.
PAL and SECAM systems
have a rate of 25 frames/s or 50 fields/s
50i
(50 interlaced fields = 25 frames) is the standard video field rate per second for PAL and SECAM television.
PAL
50 fields per second, 625 lines, odd lines drawn first
SECAM
50 fields per second, 625 lines, odd lines drawn first
NTSC
59.94 fields per second, 525 lines, even lines drawn first
PAL-M
9.94 fields per second, 525 lines, even lines drawn first
Disadvantages of progressive scan
A disadvantage of progressive scan is that it requires higher bandwidth than interlaced video that has the same frame size and vertical refresh rate. For explanations of why interlacing was originally used, see Interlace. For an in-depth explanation of the fundamentals and advantages/disadvantages of converting interlaced video to a progressive format
Benefits of interlacing
Given a fixed bandwidth instead, interlace can provide a video signal with twice the display refresh rate for a given line count (versus progressive scan video, for instance 1080i at 60 half-frames per second, vs. 1080p at 30 full frames per second). The higher refresh rate improves the portrayal of motion, because objects in motion are captured and their position is updated on the display more often, when objects are more stationary the human vision combines information from multiple similar half-frames resulting in the same perceived resolution as progressive full frames. This technique is only useful though, if the source material is available in higher refresh rates. Cinema movies are typically recorded at 24fps, and gets no real benefit from common interlacing techniques. Given both a fixed bandwidth and high refresh rate, interlaced video can also be seen as providing a higher spatial resolution than progressive scan. For instance, 1920x1080 pixel resolution interlaced HDTV with a 60 Hz field rate (known as 1080i) has a similar bandwidth to 1280x720 pixel progressive scan HDTV with a 60 Hz frame rate (720p60), but approximately twice the spatial resolution.
Advantages of progressive scan
Higher vertical resolution than interlaced video with the same frame rate. The perceived vertical resolution of displayed video is traditionally adjusted using a Kell factor coefficient. This coefficient has no fixed value and depends on display device. Its value for interlaced video is usually lower than for progressive video, when the same display device is used. When interlaced video is compared to progressive video with the same number of scan lines, interlaced video delivers lower perceived vertical resolution at a lower frame rate. Absence of visual artifacts associated with interlaced video of the same line rate, such as interline jitter. No necessity in intentional blurring (sometimes referred to as anti-aliasing) of video to reduce interline jitter and eye strain. In the case of most media such as DVD movies and video games, the video is blurred during the authoring process itself to mask flicker artifacts when used on interlace displays. As a consequence, recovering the sharpness of the original video is impossible when the video is viewed progressively. An excellent, but rarely employed countermeasure to this is when display hardware and video games come equipped with options to blur the video at will, or to keep it at its original sharpness. This allows the viewer to achieve the desired image sharpness with both interlaced and progressive displays. An example of a video game with such a feature is Super Smash Bros Brawl, where a "Deflicker" option exists. Ideally it would be turned on when played on an interlaced display to reduce interline jitter, and off when played on a progressive display for maximum image clarity. Offers much better results for scaling to higher resolutions than equivalent interlaced video, such as upconverting 480p to display on a 1080p HDTV. Scaling works well with full frames, therefore interlaced video must be deinterlaced before it is scaled. Deinterlacing can result in severe "combing" artifacts.
Problems caused by interlacing
Interlaced video is designed to be captured, transmitted or stored, and displayed in the same interlaced format. Because each frame of interlaced video is composed of two fields that are captured at different moments in time, interlaced video frames will exhibit motion artifacts known as "interlacing effects", or "combing", if the recorded objects are moving fast enough to be in different positions when each individual field is captured. These artifacts may be more visible when interlaced video is displayed at a slower speed than it was captured or when still frames are presented.
Progressive or noninterlaced scanning
a method for displaying, storing or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to the interlacing used in traditional television systems where only the odd lines, then the even lines of each frame (each image now called a field) are drawn alternately.
60i
actually 59.94, or 60 x 1000/1001 to be more precise; 60 interlaced fields = 29.97 frames) is the standard video field rate per second for NTSC television (e.g. in the US), whether from a broadcast signal, DVD, or home camcorder. This interlaced field rate was developed separately by Farnsworth and Zworykin in 1934,[1] and was part of the NTSC television standards effective in 1941. When NTSC color was introduced in 1953, the older rate of 60 fields per second was reduced by a factor of 1000/1001 to avoid interference between the chroma subcarrier and the broadcast sound carrier.
Progressive or noninterlaced scanning
is a method for displaying, storing or transmitting moving images in which all the lines of each frame are drawn in sequence.
50p and 60p
is a progressive format used in high-end HDTV systems. While it is not technically part of the ATSC or DVB broadcast standards, it is rapidly gaining ground in the areas of set-top boxes and video recordings.
Interlace/d
is a technique of improving the picture quality of a video signal without consuming extra bandwidth. Interlaced video was designed for display on CRT televisions.
25p
is a video format which runs twenty-five progressive frames per second. This framerate is derived from the PAL television standard of 50i (or 50 interlaced fields per second). While 25p captures only half the motion that normal 50i PAL registers, it yields a higher vertical resolution on moving subjects. It is also better suited to progressive-scan output (e.g., on LCD displays, computer monitors and projectors) because the interlacing is absent. Like 24p, 25p is often used to achieve "cine"-look.
72p
is currently an experimental progressive scan format. Major institutions such as Snell & Wilcox have demonstrated 720p72 pictures as a result of earlier analogue experiments, where 768 line television at 75 Hz looked subjectively better than 1150 line 50 Hz progressive pictures with higher shutter speeds available (and a corresponding lower data rate).[4] Modern TV cameras such as the Red, can use this frame rate for creative effects such as slow motion (replaying at 24 fps). 72fps was also the frame rate at which emotional impact peaked[5] to the viewer as measured by Douglas Trumbull that led to the Showscan film format.
30p
or 30-frame progressive, is a noninterlaced format and produces video at 30 frames per second. Progressive (noninterlaced) scanning mimics a film camera's frame-by-frame image capture and gives clarity for high speed subjects and a cinematic-like appearance. Shooting in 30p mode offers video with no interlace artifacts. The widescreen film process Todd-AO used this frame rate in 1954-1956.
Deinterlacing
the process of converting interlaced video, such as common analog television signals or 1080i format HDTV signals, into a non-interlaced form.
1080p
the shorthand identification for a category of HDTV video modes. The number 1080 represents 1,080 lines of vertical resolution (1,080 horizontal scan lines),[1] while the letter p stands for progressive scan (meaning the image is not interlaced). The term usually assumes a widescreen aspect ratio of 16:9, implying a horizontal resolution of 1920 pixels. This creates a frame resolution of 1920×1080. The frame rate can be either implied by the context or specified after the letter p (or i), such as 1080p30, meaning 30 progressive frames per second, or 1080i60, meaning 60 interlaced fields per second.
720p
the shorthand name for a category of HDTV video modes. The number 720 stands for the 720 horizontal scan lines of display resolution (also known as 720 pixels of vertical resolution), while the letter p stands for progressive scan or non-interlaced. When broadcast at 60[1] frames per second, 720p features the highest temporal (motion) resolution possible under the ATSC and DVB standards. Progressive scanning reduces the need to prevent flicker by filtering out fine details, so sharpness is much closer to 1080i than the number of scan lines would suggest.
1080i
the shorthand name for a format of high-definition video modes. 1080 denotes the number of horizontal scan lines—also known as vertical resolution—and the letter i stands for interlaced.
